An ink jet printer is equipped with a recording head for ejecting ink, and an ink supply apparatus for supplying ink to the recording head. In such a printer, a wiping, for example, is executed to clean the recording head which has an orifice plate on which a plurality of nozzles are formed. When the wiping is executed, ink is projected from the surface of the orifice plate through the nozzles to wet the surface of the orifice plate with ink.
In one of the examples of the conventional ink supply apparatus, a circulation flow path is composed of a first flow path which connects the inflow side of the recording head with the ink storage section and a second flow path which connects the outflow side of the recording head with the ink storage section. In addition, the first and second flow paths of the circulation flow path are connected with a bypass flow path, and a relief valve is provided in the bypass flow path. When the wiping is performed, a part of ink that flows from the first flow path toward the recording head flows to the second flow path through the bypass flow path. At this moment, the pressure of ink flowing from the ink storage section to the recording head is controlled by regulating the opening degree of the relief valve.
On the other hand, in case in which an image is formed with ink, it is desired to circulate ink between the recording head and the ink supply source. In the above-described ink supply apparatus, it is difficult to eject ink from the nozzle while ink is circulated when an image is formed. This is because that the pressure of ink in the recording head is maintained at a positive pressure when wiping is executed.